sysctl: Remove the sysctl system call

sysctl: Remove the sysctl system call

This system call has been deprecated almost since it was introduced, and
in a survey of the linux distributions I can no longer find any of them
that enable CONFIG_SYSCTL_SYSCALL.  The only indication that I can find
that anyone might care is that a few of the defconfigs in the kernel
enable CONFIG_SYSCTL_SYSCALL.  However this appears in only 31 of 414
defconfigs in the kernel, so I suspect this symbols presence is simply
because it is harmless to include rather than because it is necessary.

As there appear to be no users of the sysctl system call, remove the
code.  As this removes one of the few uses of the internal kernel mount
of proc I hope this allows for even more simplifications of the proc
filesystem.

Cc: Alex Smith <[email protected]>
Cc: Anders Berg <[email protected]>
Cc: Apelete Seketeli <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Chee Nouk Phoon <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: Christian Ruppert <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: Harvey Hunt <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Hongliang Tao <[email protected]>
Cc: Hua Yan <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: John Crispin <[email protected]>
Cc: Jonas Jensen <[email protected]>
Cc: Josh Boyer <[email protected]>
Cc: Jun Nie <[email protected]>
Cc: Kevin Hilman <[email protected]>
Cc: Kevin Wells <[email protected]>
Cc: Kumar Gala <[email protected]>
Cc: Lars-Peter Clausen <[email protected]>
Cc: Ley Foon Tan <[email protected]>
Cc: Linus Walleij <[email protected]>
Cc: Markos Chandras <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Noam Camus <[email protected]>
Cc: Olof Johansson <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Phil Edworthy <[email protected]>
Cc: Pierrick Hascoet <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Roland Stigge <[email protected]>
Cc: Santosh Shilimkar <[email protected]>
Cc: Scott Telford <[email protected]>
Cc: Stephen Boyd <[email protected]>
Cc: Steven J. Hill <[email protected]>
Cc: Tanmay Inamdar <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Wolfram Sang <[email protected]>
Acked-by: Andi Kleen <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Signed-off-by: "Eric W. Biederman" <[email protected]>